We don’t use them for brewing, just drinking, I think they are just too narrow to get any good movement with the leaves and the other ceramic one I have doesn’t have a lid (all three I got from work for free as lids got dropped but I was able to replace the one broken one from the pair when it’s partner got dropped later).

However I do have a glass infuser mug from a Teavana gift set on clearance. It has a glass strainer with slits on the bottom and I use that for nearly all my whites and greens whether I’m brewing western or gongfu style, I simply double the leaf and pour half the amount of water.

I’ve had a few infuser mugs and this one has worked the best.http://i179.photobucket.com/albums/w309/buddha614/IMG_2587.jpg
It has many more smaller holes in it than the others I have bought, and I think that makes the difference. Like a few people already said, tea leaves can make it through the big holes. I picked this one up in China so it might be hard to find something similar, but it might be worth trying find one.